Fact of the Day .CA

The Light Spectrum

Why do we see the colours that we see?  Why do some things appear white, blue, yellow, or purple?  Well I hope to shine some light on this question.  Some of us already know about the light spectrum, and that humans can only see a small proportion of it.  This small range is aptly named “visible light”.  Leave it to humans to name things with respect to themselves.  I say this because some animals can see outside of this range.  Bees, for example, are capable of detecting the higher-frequency Ultra-Violet light waves.  Additionally, the visible range of a Mantis Shrimp starts in UV and reaches down into the Infra-red.  But getting back to us humans.  In the visible light spectrum each colour is characterized by its own specific light wavelength.

So back to our original question, why do we see the colours that we do?  The process is more complex than I am going to get into for the purpose of this article.  Basically certain materials absorb specific wavelengths of light and reflect the rest.  This reflected light it what is transmitted to our eye and perceived as the colour of that object.  So, plants which appear green are actually reflecting green light and not using it at all.

So here’s some scientific proof that your mother was right yet again.  White is the best colour of clothes to wear on a hot, sunny summer’s day, and black is the worst.  When we see white it is because all of the different colour wavelengths are reflected from the material, whereas black is a result of all these wavelengths being absorbed, resulting in heat build up from the light energy.  This has been adapted into the animal kingdom and is very important for animals in polar regions such the polar bear or Harp seal pups.  Their fur is white and their skin black.  The white fur reflects the sun down to the black skin where it absorbs the light energy which is then transferred into heat energy.  As you can see this would be very advantageous for an animal in order to stay warm in such a cold climate.